Twitter co-founder Biz Stone has stated that the popular micro-blogging service is definitely not on sale.

We have heard several rumors in the market related to potential talks going on. First it was Google and then later it was Apple.

Stone added in his latest statement that they are focusing on adding new features and functionalities to the service.

They are also aiming to remain independent while the company grows to new heights.

Twitter incidentally still has no revenue model. It remains to be seen if they can continue growing at this pace without generating any money from the service.